Different approaches for enhancing audio signals in relation to hearing impairments have been suggested. For example, isolation and amplification of speech in an audio signal and/or suppressing of sound that interfere with speech in an audio signal have been suggested. However, such amplification does not specifically take into account hearing impairment in specific frequency ranges. For example, one type of hearing impairment involves high frequency hearing loss such that the audibility of a person drops beyond a crossover frequency. For such hearing impairments, amplification is not sufficient to increase the audibility in the higher frequencies.
Methods have also been suggested for frequency lowering, for example by frequency compression where input frequencies in a frequency interval from a lower frequency limit below a crossover frequency to a upper frequency limit above the crossover frequency are compressed to output frequencies in a frequency interval from the lower frequency limit to the crossover frequency. Furthermore, frequency transposing has also been suggested where frequency components of a target range below a crossover frequency are replaced by corresponding frequency components of a source range above the crossover frequency and where frequency components of the target range are combined with corresponding frequency components of the target range.
Frequency transposing methods include methods such as disclosed in U.S. Patent Application with Pub. No. US 2014/0105435.
All techniques for frequency transposing suffer from issues relating to loss of relevant frequency components in the source range and/or in the target range. Hence, there is a need for further methods for enhancing an audio signal in relation to a hearing impairment in certain frequency bands.
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